A communication system including plural baseband units (BBU), plural radio remote heads (RRH), and plural relay devices is known.
In a radio communication system, it is often difficult to change the BBU as a communication destination of the RRH. In this case, the communication traffic in a radio area often concentrates on a specific BBU. Therefore, the transmission rate in the radio area often becomes too low if a communication system appropriate to an amount of communication traffic in the radio area and the worst value of the transmission rate between the BBU and the RRH is not prepared. Thus, CAPEX and OPEX often become too high. CAPEX is an abbreviation of capital expenditure. OPEX is an abbreviation of operating expenditure.
Increase in the number of radio areas (in other words, increase in the radio area density) is often carried out along with reduction in size of the radio areas. The radio area density represents the number of radio areas per unit area. As the radio area density increases, the number of BBUs on which the communication traffic concentrates also increases. In other words, as the radio area density increases, the use efficiency of the BBUs and the RRHs lowers. Therefore, in the radio communication system, the communication traffic is distributed by allowing change of the BBU as the communication destination of the RRH. As a result, the use efficiency of the BBUs and the RRHs is enhanced.
The communication system couples the BBUs and the RRHs via plural relay devices. If failure occurs in a BBU as the communication destination of a certain RRH, the communication system switches the communication destination of this RRH to another BBU prescribed in advance.
As one example of the related art, Japanese Laid-open Patent Publication No. 2014-121054, Japanese Laid-open Patent Publication No. 2009-231970, Japanese Laid-open Patent Publication No. 2014-110574, and Japanese Laid-open Patent Publication No. 2011-114689 are known.